This paper presents a benchmark exercise for the seismic assessment of unreinforced masonry (URM) buildings as a follow-up of a blind prediction test organized in the context of the European Conference of Earthquake Engineering Series. The blind prediction exercise was aimed at better defining the open issues in current procedures for modeling and performing seismic analysis of URM buildings, by highlighting the uncertainty that can influence the results. This work presents an overview of the approaches used by different research teams and the scope of predictions. The benchmark structure was a three-story building with traditional European architecture from which two Cases were considered: A) stone masonry walls and flexible horizontal diaphragms and B) brick masonry walls and rigid horizontal diaphragms. A wide range of approaches was used by the participating teams concerning modeling strategies, methods of analysis and criteria for the attainment of limit states, which are here addressed as potential sources for the dispersion of predictions. The results were compared in terms of capacity curves, predicted failure mechanisms compatible with the fulfillment of limit states of near collapse and damage limitation, and related minimum values of peak ground acceleration (PGA). The results show an overall good agreement for damage patterns and collapse mechanisms in both benchmark structures, presenting some differences in the type of failure mode and its extent. However, the scatter of predicted capacity curves and critical PGAs is very high, especially for the Case with brick masonry and rigid diaphragms, indicating that clearer procedures in the building codes are required for professionals.

An experimental programme was conducted on six different batches of unreinforced masonry (URM) considering different unit-mortar combinations to study their behaviour under torsional shear. Experiments performed included a specific characterisation test to measure the torsional shear strength of URM bed joints. Dilatancy measurements during both direct and torsional shear testing of masonry were recorded. Refined finite element modelling was then performed to evaluate whether parameters evaluated from standardised direct shear tests on masonry triplets can be used to estimate the torsional shear strength of URM bed joints. A possible mechanism by which dilatancy can increase the torsional shear resistance of bed joints without affecting the external level of applied normal force is also presented. Based on both experimental and numerical findings, a rational mechanics based formula to evaluate the torsional shear strength of URM bed joints is proposed and validated. This formula represents an improvement on currently used empirical formulation correlating the torsional shear strength of a URM bed joint to their flexural tensile strength.

In this paper, a dataset collecting the results of in-plane cyclic tests on unreinforced masonry piers, carried out within different research projects, is presented. The dataset includes brick and block walls with different materials, bed-and head-joint typologies, dimensions, boundary conditions and vertical applied loads. The development of such dataset aims at providing a tool for the improvement of the understanding and the evaluation of the main parameters that may influence and govern the lateral response of the URM piers under seismic excitation. A preliminary investigation on the in-plane lateral strength and displacement capacity, being two of the most significant parameters used in seismic analyses for the design and assessment of masonry buildings, has been proposed. The dataset, that already groups several specimens, is freely shared and might be continuously updated. This source of information of consistent and reliable test results represents a necessary step into the process of definition of shared rules within the scientific and technical community, in particular for the improvement of codified criteria, analytical and numerical models and testing procedures.